1. Field of the Invention
The present invention relates to an apparatus and a method for transmitting a multimedia frame in a broadcast system. More particularly, the present invention relates to an apparatus and a method for transmitting a multimedia frame through a heterogeneous network in a broadcast system supporting a multimedia service based on an internet protocol.
2. Description of the Related Art
A Moving Picture Experts Group-2 Transport Stream (MPEG-2 TS) is typically used for transmitting a multimedia content in a broadcast network. The MPEG-2 TS is used as a representative transmission technology for transmitting bit streams (a plurality of encoded video bit streams) in which a plurality of broadcast programs are multiplexed in a transmission environment having an error. For example, the MPEG-2 TS is suitable for being used for broadcasting a digital TV signal in a multimedia age.
FIG. 1 illustrates a structure of layers for supporting the MPEG-2 TS according to the related art.
Referring to FIG. 1, layers for supporting the MPEG-2 TS include a media coding layer 110, a synchronous (sync) layer 120, a delivery layer 130, a network layer 140, a data link layer 150, and a physical layer 160.
The media coding layer 110 and the sync layer 120 are constructed in a format by which media data may be easily used in the basic unit of a record or a transmission. The delivery layer 130, the network layer 140, the data link layer 150, and the physical layer 160 record a data block (e.g. “AU”) of a format constructed by the sync layer 120 in a separate recording medium or configure a multimedia frame for a transmission. The configured multimedia frame is transmitted to a subscriber terminal through a predetermined network.
For this purpose, the sync layer 120 includes a fragment block 122 and an access unit 124. The delivery layer 130 includes an MPEG-2 TS/MP4 132, an RTP/HTTP 134, and a UDP/TCP 136.
However, the MPEG-2 TS has several limitations in supporting a multimedia service. The limitations of the MPEG-2 TS include one-way communication, an inefficiency of a transmission due to a fixed frame size, and a generation of unnecessary overheads in a transmission using an Internet Protocol (IP) and a transmission protocol specialized for an audio/video.
Accordingly, a MPEG Media Transport (MMT) standard is newly proposed in the MPEG as a multimedia transmission technology for supporting a multimedia service based on an MPEG technology. The MMT standard is proposed by the MPEG in order to overcome the limitations of the MPEG-2 TS.
For example, the MMT standard may be applied for efficiently transmitting hybrid content through a heterogeneous network. Hybrid content denotes a set of contents having a multimedia element by a video/audio/application. The heterogeneous network denotes a network where a broadcast network and a communication network coexist.
The MMT standard intends to define a transmission technology closer to an IP, which is a basic technology in a transmission network for a multimedia service. Accordingly, the MMT standard is to representatively provide an efficient MPEG transmission technology in a multimedia service environment changed based on the IP, and its standardization is in progress together with continuous research. A method is desired that provides effective MPEG transmission technology in a multimedia service environment intending to provide a hybrid network and hybrid content in the MMT standard.